WO2017153694A1

WO2017153694A1 - Insulating thermal barrier having hot and cold pcm

Info

Publication number: WO2017153694A1
Application number: PCT/FR2017/050541
Authority: WO
Inventors: Fabrice Chopard; Cédric HUILLET; Fanny Geffray
Original assignee: Hutchinson
Priority date: 2016-03-11
Filing date: 2017-03-09
Publication date: 2017-09-14
Also published as: CN109154477A; FR3048765B1; EP3427000A1; EP3427000B1; US20190093960A1; FR3048765A1; US11009299B2

Abstract

Disclosed is a thermal barrier (3) for helping maintain a temperature in a volume and/or at least one interior structural component (1) surrounded by said barrier. The barrier comprises a first component (3a) containing at least one phase change material (PCM) that changes its state at a first temperature, a second component (3b) containing a PCM that changes its state at a second temperature which is different from the first temperature, and a third, thermally insulating component (5a, 5b) that is placed between the first and second components containing a PCM or outside the second component (3b).

Description

INSULATING THERMAL BARRIER HOT AND COLD MCP

The present invention relates to the field of thermal management.

Particularly concerned is a thermal barrier for maintaining, in a volume and / or at least one inner structural member surrounded by this barrier, a temperature in a predetermined range while the barrier is placed in an external environment subjected to a non-constant temperature.

Also concerned is an assembly comprising at least one such interior volume and a wall provided with this thermal barrier which will then surround said volume.

Among the targeted applications, we will note:

- that of the thermal management of an electric storage battery,

or, on a motor which typically heats when it is running, that of a device for encapsulating a part of this motor, for example all or part of an engine block.

In some cases it is appropriate to be able to:

isolating the said volume and / or the said internal structural element from the external environment,

and / or act on the propagation of a heat flux to or from this volume or element,

and / or smoothing the temperature in said volume or in at least part of a wall with which it can be in contact,

- Or instead promote a rise in temperature in the volume, - or promote a temporary heat storage in the barrier.

It is in this context that it is proposed here that the thermal barrier comprises:

- from the inside (where is located said interior volume or the element which is disposed there) towards the outside: a first element containing at least one MCP material storing or yielding thermal energy by state change and having a first state change temperature, and then

a second element containing at least one MCP material storing or transferring thermal energy by a change of state and having a second change of state temperature, the second change of state temperature being different from the first one,

and a third element, a porous thermal insulator, disposed between the first and second elements containing an MCP material or outside said second element.

For the performance of the thermal insulation, it is recommended that the third heat insulating element contains a porous material (or nano-porous).

And again for this purpose and / or for potentially mechanical purposes, it is furthermore recommended that this third thermal insulating element be arranged in a sealed envelope, to define at least one insulating panel under a controlled atmosphere, PIV.

Indeed, the PIV panels are known as performing in terms of thermal insulation. But their manufacturing or implementation conditions are often imperfect. Also, a solution proposes here an MCP / PIV barrier, with said first and second elements containing one or more phase change materials (PCM), this barrier being conditioned so as to comprise at least one closed outer envelope constituted at least one conformable (eg flexible) foil sealed to said MCP materials and containing the first, second and / or third elements.

To further promote the reliability and the mechanical strength, it is possible for said one or more conformable sheets to be metallic, and typically of a thickness of 0.05 mm to 5 mm.

With such solutions, metal-based or not, we will associate a high performance thermal insulation with a unique packaging (mono or multi-cell, see below) to set up thermal management where it is desired.

Especially with a solution of PIV insulating panel with metal walls (including alloy, such as stainless steel or aluminum), it will even be possible to deviate from a flat PIV plate, providing that said first , second and third elements are molded into a three-dimensional shape and interposed between two metal walls sealed together in airtight manner, over their entire periphery, to exhibit a leakage rate of less than or equal to 10 ^-4 Pa.m ³ / s, at the location of the seals.

To further optimize the thermal protection, it may be useful for at least one of the first and second thermal barrier elements to contain a plurality of MCP materials storing or releasing phase change thermal energy between liquid and solid, and having different state change temperatures.

Thus, it will be possible to stagger the barrier effects to the passage of disruptive thermal flows from maintaining the temperature of said interior volume.

In addition, several thermal management situations may occur, depending on the applications.

First, in many cases, including thermal management of an electric battery housed in the interior volume, or a passenger compartment, it will be recommended that the change of state temperature (s) of the MCP material (s) of the first element (s) lower than the changeover temperature (s) of the MCP material (s) of the second thermal barrier element, so that at certain temperatures heat flows from from outside and reaching one and / or the other of said elements are braked in their progression from the outside to the inside, by change of state of the MCP (s) in the said (s) element (s) achieved. This is a complement or an alternative to the aforementioned barrier effect, each element playing at best its role as a hot flow or a cold flow.

And having a thermal barrier where the at least some of the state change temperature (s) of the first element MCP material (s) will be lower than the temperatures of said predetermined temperature range to be maintained, may even be even more profitable, as detailed below.

In this regard, it can now be noted that, if the MCP of the inner element crystallize (by cold penetration into the barrier, for example after its installation on a vehicle intended to be parked on cold nights at night). 'outside'), they will be able to recharge reluctantly in the liquid state, when the moment comes, in contact with a heat flow created by the exchange with the interior volume or with the element which is disposed there: hot flow in the case for example of a battery which, while operating, releases heat.

Including in these situations, and to best ensure the complementarity of the barrier effects vis-à-vis the hot and cold, we can choose:

that the highest state change temperature in said first thermal barrier element is equal, within approximately 5 ° C, to the lowest temperature of said predetermined temperature range to be maintained,

and / or that the lowest state change temperature in said second element of said thermal barrier is equal, within about 5 ° C, to the highest temperature of said predetermined temperature range to be maintained.

In the case of an assembly comprising at least one volume surrounded by a wall provided with the aforementioned thermal barrier, providing electric battery cells as an element present in the volume whose temperature is to be regulated may be very useful . In particular, at least one cell of this battery may then comprise an outer envelope provided with said thermal barrier.

Moreover, this situation will be a good example of a favorable case in which such a thermal barrier assembly will comprise means for temporarily supplying the said internal volume of a thermal energy, in heat exchange with the said first element containing at least one MCP material. , to then promote a phase change of said MCP material of this first element.

Bringing air conditioning into a cabin surrounded at least locally by this thermal barrier could be another favorable case.

In the case of a hot air-conditioning, and in an application to an electric battery, for example, it is even advisable for the means of temporarily supplying thermal energy and said interior volume to communicate with each other so that said energy is provided in this volume at a temperature greater than or equal to the temperature (s) of change of state of the MCP material or materials of the first element, in heat exchange with the MCP or these materials, to then promote their liquefaction.

In cold outdoor weather, they will be regenerated, ready to solidify in the face of cold from outside.

It is possible, however, that, in a second category of situations, it is necessary to favor / accelerate an increase in temperature in the interior volume, for example for the thermal management of a heat engine that is locally surrounded by said barrier thermal, or a pollution control system on a vehicle exhaust line in which a rapid thermal rise is desired.

In such cases, it will preferably be chosen that the at least one change of state temperature of the MCP material (s) of the first (interior) element is (are) lower than the temperature (s) of the state change of the MCP material (s) of the second element (plus outside), for braking, by change of state, a heat transfer from the inside to the outside resulting from the supply into the internal volume of a fluid at at least a temperature greater than or equal to that (s) of change of state of the MCP material (s) of said first element, thus favoring (or accelerating) an increase in temperature in the interior volume.

In this second category of situations, we can usefully predict that the thermal barrier is placed in an external environment:

periodically warmer (due to the heat generated by the operation of the engine) than the change of state temperature (s) of the MCP material or materials of the second element,

and with which this or these MCP materials of said second element will be placed in heat exchange,

to then promote their liquefaction (s).

Thus, it will be possible to ensure the regeneration of the outermost MCPs when heating an engine, for example an engine encapsulated at least locally by the barrier presented here.

In all the preceding cases, it may be advantageous for said third thermal insulating element to be disposed between the first and second elements, respectively inside and outside the thermal barrier.

Indeed, although not essential, this will distinguish well the two blocks of MCP, respectively cold and hot, each with its function, the intermediate thermal insulation to slow the influence of one on the other.

A priori in all targeted applications, it may further be advantageous if, if several MCP materials having different state change temperatures are provided in at least one of the first and second elements, these MCPs are rather dispersed in a matrix that is arranged in several layers of materials each containing a said MCP material. Thus thermal management will be obtained by zones, rather than by layers, thus improving the efficiency of this management or at least the manufacture of the barrier.

From the foregoing, it will be understood that, translated in terms of thermal management method, the solution presented above has the particularity that:

- if only the thermal barrier is aimed at:

first, the barrier will be made,

- Then it will be arranged around said inner volume, or the element disposed therein, so that said first and / or second thermal barrier elements brake, by changes of state, a heat flow from outside;

- and, if the aforementioned set is referred to:

- the thermal barrier will always be realized, with PCM materials with phase change between liquid and solid,

- Then it will be arranged around said inner volume, or the element disposed therein, again such that said first and / or second thermal barrier elements brake, by changes of state, a heat flow coming from outside ,

furthermore, once the change in states of the at least one MCP material of the first thermal barrier element has been achieved, a new change in its state will be promoted by a temporary supply of thermal energy from said means (20,22; 26) temporary supply of thermal energy.

If necessary, the invention will be better understood and other characteristics, details and advantages thereof will become apparent upon reading the following description, given by way of non-limiting example and with reference to the accompanying drawings, in which: which :

- Figure 1 is a schematic section illustrating a thermal barrier half according to the invention; FIG. 2 schematizes the application of a thermal barrier according to the invention to cells of a battery pack;

FIG. 3 is a diagram of the operating mode of a thermal barrier according to the invention;

FIGS. 4 to 7 schematize the double thermal barrier operation of the proposed solution, in an application, for example, prismatic and "new type" batteries, FIGS. 4,5, and comfort management in a motorhome interior. Figures 6.7; it could also be the cabin of a truck, or a greenhouse;

FIGS. 8, 9 are diagrams in perspective of the barrier, in two different embodiments;

FIGS. 10-13 schematize in section various embodiments of thermal barrier sections which, at least at the location of the aforementioned pockets, may each have the internal structure of FIG. 1, or a structure as described below,

FIG. 14 schematizes hot and cold MCPs respectively dispersed, for the first on one side, for the second on the other side, with a thermally insulating intermediate layer,

and FIG. 15 schematizes the double thermal barrier operation of the proposed solution, in a motor shield application.

In the following we will treat, as non-limiting examples:

- the case of a storage battery,

- the case of a motorhome interior,

- The case of an external thermal protection device of an engine, respectively provided with a thermal barrier meeting all or part of the above characteristics.

As a unit in the approach followed, note that the thermal management solution proposed here should preferentially be autonomous, light and compact.

It should also be noted that the industry is currently invited to speed up the introduction of new technologies that can reduce emissions of pollutants, smooth any occasional increases in charges or thermal gradients compared to a nominal operating dimensioning, or propose solutions to offset the return of available energy at another time, or promote operation of an element in its optimum operating temperature range.

All or part of the above solution to MCP materials and thermal insulation (s) must help achieve this.

At any end, it is confirmed that a phase change material - or PCM, or PCM in English - designates a material capable of changing its physical state, between solid and liquid, within a restricted temperature range of -50 ° C and 60 ° C (battery) or 160 ° C (motor encapsulation). The transfer of heat (or heat transfer) can be done by using its Latent Heat (CL): the material can then store or give up energy by simple change of state, while maintaining a substantially constant temperature, that the change of state.

The thermally insulating material (s) associated with the MCP (s) may be a "simple" insulator, such as glass wool. But it will certainly be preferred, a foam, for example polyurethane or polyisocyanurate, or even more favorably a porous thermally insulating material, or even nano-porous, disposed in a sealed envelope, to define at least one PIV panel.

Again for any purpose:

- "PIV" means an enclosure under "controlled atmosphere", that is to say either filled with a gas having a thermal conductivity lower than that of the ambient air (26mW / mK), or in "depression ", Therefore under a pressure lower than the ambient pressure (<10 ⁵ Pa). A pressure between 10 ° Pa and 10 ⁴ Pa in the chamber may in particular be suitable. The enclosure may contain at least one heat insulating material a priori porous (pore sizes less than 1 micron). In this case, the performance of the thermal management to be assured will be further improved, or even the weight overall decreased compared to another insulator. Typically, VIP (VIP) panels are thermal insulators in which at least one porous material, for example silica gel or silicic acid powder (SiO2), is pressed into a plate and surrounded, under partial air vacuum. , a gas-tight wrapping sheet, for example plastic and / or laminated aluminum. The resulting vacuum typically lowers the thermal conductivity to less than about 0.003 / 0.01 W / mK under the conditions of use. An insulation efficiency 3 to 10 times higher than that of more conventional insulating materials is thus obtained. A thermal conductivity λ less than 0.008 / 0.01 W / mK is hereby expected, preferably;

- "porous" means a material having interstices allowing the passage of air. Open cell porous materials therefore include foams but also fibrous materials (such as glass wool or rock wool). The passage interstices that can be described as pores have sizes of less than 1 or 2 mm so as to ensure good thermal insulation, and preferably at 1 micron, and preferably still at 1 to 2 × ¹⁰ -8 m (structure almost nanoporous), for particular issues of resistance to aging and therefore possible lower depression in the PIV envelope;

- "conformable" is a structure that can be deformed, for example bend, by hand;

- "sealable" relates to a weldable connection, in particular heat-sealable, or even solderable, with sheets or films (finer), in particular.

Regarding these PIV panels and MCP materials, it is also noted that they do not seem to meet the expectations of the market so far. In particular, their implementation in the field is a problem, especially their conditioning. There are solutions proposed here that palliate this situation.

Thus, whatever the external conditions (hot or cold) to a certain extent, the invention proposes to participate in maintaining the temperature of a volume and / or an element disposed therein. (a battery pack for example) in an optimal temperature range, from a standalone system.

Figure 1 shows the principle of the developed solution.

Suppose a block, volume (hollow space) or internal structure, for example, which produces heat at certain operational moments and not at others, such as an electric battery that heats when its cells produce electricity.

The inner block 1 is surrounded by a thermal barrier 3. "Surrounded" implies that the inner volume 1 is bordered by the barrier 3, directly or indirectly (for example with the interposition of walls, including an insulating thermal wall, such as that 5a or 5b - see below), on at least part of its periphery, for example on one side at least.

It is intended to maintain the temperature of, or in, the block 1 in a predetermined range while the barrier 3 is placed in an external environment 4 subjected to a non-constant temperature, such as typically an ambient air between -20 / -30 ° C and 50 ° C.

For this purpose, the thermal barrier 3 comprises at least, from the inside (INT) to the outside (EXT):

at least one first element 3a containing at least one MCP material and having a first phase or state change temperature

(physical),

at least one second element 3b also containing a MCP material storing and having a second change of state temperature, the second change of state temperature being greater than the first, at least one third thermal insulating element, two example:

5a, 5b disposed between said first and second members 3a, 3b and / or outside said second member 3b.

The elements 3a, 3b will contain (at least) a MCP material in the sense that they will be made exclusively or not with material (pure) or more likely with (at least) a MCP material placed in a matrix, with charges. As a constitution of one or the other of these elements 3a, 3b, it will be possible to provide a rubber composition as described in EP2690137 or in EP2690141, namely in the second case a crosslinked composition based on at least an "RTV" silicone icon elastomer vulcanized at ambient temperature and comprising at least one MCP material, said at least one silicone elastomer having a viscosity measured at 23 ° C. according to the ISO 3219 standard which is less than or equal to 5000 mPa.s. In this case, the elastomer matrix will be mainly constituted (ie in an amount greater than 50 phr, preferably greater than 75 phr) of one or more silicone elastomers "RTV". The thermal MCP material may consist of n-hexadecane, eicosane or a calcium salt, all having melting points below 40 ° C.

The other element 3b or 3a may be based on paraffin, eutectic fatty acid (myristic-capric) or hydrated salt eutectic (calcium chloride + potassium). Other possibilities exist, such as a PCM impregnated in a porous network.

Assume operational conditions where the block 1 is a volume containing, as shown schematically in Figure 2, the cells 2 producing electricity of a battery where it is ideally desired to maintain the temperature, TB, between 25 ° C and 35 ° C. EB will be the operating state of the battery: OFF (in operation) or ON (when stopped). The barrier 3 will then be favorably associated with the wall 6 of a casing, or casing, 8 in which the cells 2 may be enclosed, whether or not they are packaged together. In practice, and in particular if a pocket constitution 13 is retained (see below), the barrier 3 may come to double the wall 6 (plastic, composite, or even metal) or be integrated with it (for example by molding).

Suppose also that means of conduction and convection (such as metal fins defining between them channels of air circulation) are favorably present to seek to maintain this range of internal temperature, if the temperature of the external environment also evolves between 25 ° C and 35 ° C, and as long as the battery is running (engine equipped with this battery not stopped), being however specified that the efficiency of the barrier 3 is effective that such means are provided or not.

Since in fact the temperature TA of the external environment can vary between -20 ° C and 45 ° C, several disruptive situations may occur, breaking the internal / external thermal equilibrium, especially when said convection means are s' stop (typically when the engine is stopped). So :

if external medium 4 has a temperature greater than 35 ° C. (hot time for example), then it will begin to have an increase in internal temperature, in block 1,

- If the external medium 4 has a temperature below 25 ° C, then it will instead begin to have a decrease in said internal temperature.

In order to limit these incoming or outgoing heat flows (arrows 7a, 7b, FIG. 1), one has thus first set up one, here several, thickness of insulation or super-thermal insulation 5a, 5b. A thermally insulating layer 5a is thus placed around the second element 3b with MCP material. And a thermally insulating layer 5b is placed between the first and second MCP material members 3a, 3b. The layer 5a could also be on the inside of the first inner thermal barrier element (against the layer 3a8 in FIG. 1).

In any case, without the layers MCP, respectively hot 3b and cold 3a, which will store energy by melting (liquefaction) and restore it by crystallizing, the action of the thermal insulation will remain insufficient.

Hence the interest of one, and preferably several layers 3a based on "cold MCP" with in the example one or more crystallization temperatures Te <= 25 ° C and one, and preferably several layers 3b based of "hot MCP", with in the example one or more melting temperatures Tf> = 35 ° C.

Their main common function is to participate in maintaining permanently a temperature of the block 1 in the desired range: here battery temperature between 25 and 35 ° C.

The operational technical functions are as follows (see diagram figure 3):

- FT1: control the action of ambient cold (for TA = <25 ° C) and slow down the spread of cold to the interior volume,

- FT2: control the action of the ambient heat (for TA> = 35 ° C) and slow down the propagation of heat towards the interior volume,

- FT3: limit heat transfer from the inside to the outside (for TB = <35 ° C in the case of a battery).

A constraint imposed is that this solution is light, compact and operates without external energy supply to the battery or electrical energy collected by the battery. Barrier 3 will then be considered as being autonomous.

Their evolutions are as follows:

- a) the "cold MCP": the MCP melt or crystallize each at their temperature of change of state, with melting temperatures all

<25 ° C:

- Thus, these layers 3b absorb and store the so-called cold energy (yielding heat of crystallization) when they crystallize, thereby delaying the spread of cold environment 4 to the battery,

- and release stored cold energy (or absorb and store heat by liquefaction) when MCP melts.

Suppose that after a phase of operation occurs a shutdown of the battery (EB becomes OFF). The layers of "cold MCP" have melted, they are liquid. The internal temperature in the block 1 is then greater than 25 ° C. During the following hours, the evening arriving for example, the barrier 1 will go down in temperature due to low outside temperatures TA which can for example be between -2 ° C and 10 ° C. The objective of the layers 3a based on cold MCP is then to delay this drop in internal temperature by storing crystallization energy. The set of cold MCP layers 3a associated with the insulation 5a and / or 5b must make it possible to limit the temperature drop of the volume 1.

When the battery will re-run (EB becomes ON), quickly TB> = 25 ° C. The cold MCP layer (s) 3a will then liquefy, preventing (limiting) that the heat of the battery leaves out, as long as TB is not excessive. In addition, this heat production and its dissipation in the barrier will then be used to regenerate the cold MCP which will have crystallized during the shutdown phase;

- b) the "hot MCP": the MCP melts or crystallizes each at their change of state temperature, with melting temperatures of> = 35 ° C:

- Thus, these layers 3a absorb the thermal energy when they melt, thereby delaying the propagation of the hot energy from the environment 4 to the battery (block 1),

- and release the hot energy that they stored, when their MCP crystallized for T <35 ° C.

Suppose it is hot outside: room temperature TA = 38 ° C. Layers 3b based on "hot MCP" liquefy, delaying the propagation of heat to the battery, absorbing the hot energy. This helps maintain the battery in its range of favorable operating temperatures (25 ° C to 35 ° C).

In the evening, or later, if TA <= 35 ° C, this / these layers based on "hot MCP" will / will recrystallize, by natural convection at least.

If then EB (re) becomes ON (the battery produces electricity again), for example the following morning, when the vehicle will be restarted, and that TB> = 35 ° C (no such means of conduction and of convection, or immediate response problem) the crystallized layers 3a will be able to absorb some of the heat produced by the battery, thus promoting its operation.

The above confirms the interest first:

the two layers 3a and 3b have at least two compositions based on MCP material having individually different state-changing temperatures: 25 ° C and 35 ° C respectively, in the example,

and therefore even favorably that at least one of the first and second elements 3a, 3b comprises several layers of materials each containing a MCP material "cold MCP" and "hot MCP", with respectively the layers such as 3b1, 3b2 and 3a1. ..3a8.

In the latter case, the advantage of providing state change temperatures that will grow from the first innermost layer to the outermostmost layer will be to stagger the effects of expected thermal barriers.

Thus, we can provide:

at least two layers 3b1, 3b2, thus with two temperature changes of state, for example one, of melting, lower Tf1 = 35 ° C for the innermost layer 3b2 and another, higher Tf2 = 40 ° C for the outermost layer 3b1;

more than two layers, for example eight layers, 3a1... 3a4,... 3a8, with therefore as many changeover temperatures, ranging for example in increments of 5 ° C., between 20 ° C. ( outermost layer 3a1) and -15 ° C (innermost layer 3a8).

An advantage of the thermally insulating layer 5b interposed between the layers 3a and 3b is to limit heat transfer between the layers "cold MCP" and "hot MCP", leaving each act as fully as possible, including the effect smoothing. A comparable subject can be applied to the layer 5a, here the outermost of the barrier 3, which forms the first (sense 7a) or last (sense 7b) obstacle insulating. As for the distribution in (multiple) sub-layers of the MCP materials, it will, industrially, probably be replaced by the use of several MCP materials having different state change temperatures and which will be dispersed in a matrix (see solution figure 14 FIG. 4 schematizes the abovementioned procedure, in the typical case where the barrier 3 surrounds, preferably on all sides, the internal volume 1 in which is disposed a pack 20 of prismatic battery cells 2.

Examples of solid state-to-liquid state change temperatures of the MCPs present in each layer (or dispersed, see below) of the first and second MCP material elements 3a, 3b are indicated.

As shown in the figure, these change of state temperatures are generally increasing from the inside (INT) to the outside (EXT). A concordance between the temperatures T1 on the one hand and T2 on the other hand, with T2 greater than T1 is to be noted, on the basis of the explanations that follow.

In this case of prismatic cells 2, the predetermined range of temperatures to be maintained in operation, when the switch 22 of the circuit which controls the operation and the shutdown of the battery is closed, is between 25 and 35 ° C. (in the optimum, it could be expanded by 5 ° C).

To ensure this maintenance, it must be a barrier to cold or heat exceeding these terminals and coming from outside 4 (EXT).

Suppose initially all the "recharged" MCP that is to say solid state for the MCP hot and liquid for the cold MCP.

If it is too hot, for example 38 ° C, the MCP then liquefied from the marked layers 45 ° C and 40 ° C, delayed the flow of heat entering from the outside to the inside.

If, for example, at night, the outside temperature drops to 10 ° C, it is then the cold MCP that will crystallize, delaying or thus slowing down the temperature drop of the battery pack. At the same time, the "hot" MCPs of the second element with MCP material 3b will then all "recharge", crystallizing, if care has been taken that the change of state temperature T2 of the MCP material of the layer 3b3 in contact with the outside of the intermediate insulation 5b is equal (within 10%) to the maximum temperature (T2) of the range to be maintained (here 35 ° C), the change of state temperatures of all the other MCP of the second element 3b being greater than T2. The highest state change temperature of these MCPs (here 45 ° C, outermost layer 3b1) is lower (or equal) than the assumed maximum outside temperature, here 50 ° C.

In the internal face, the last MCP, here of the layer 3a4, will also be able to "recharge", as all other MCP of the first element 3a, by liquefying:

if it has been taken care that the temperature of change of state T1 of the MCP material of the layer 3a1 to the internal contact of the intermediate insulator 5b is equal (within 10%) to the minimum temperature (T1) of the range to be maintained (here 35 ° C), the change of state temperatures of all the other MCPs of the first element 3a being less than T1,

and if, at a given moment, the MCPs of the first element 3a have been placed in thermal exchange with the heat flux 24, here hot, generated in the volume 1 by the battery in operation.

Thus, so that after a cold period (outside temperature lower than 25 ° C in this case) where they have (at least) delayed the propagation of this cold to the battery 20, the MCP of the first barrier element is liquefied again , we will let the heat released by the battery that works reach the temperature T1, or between T1 and T2.

Typically, after the operational operating time of the battery interrupted here by the opening of the switch 22, the stream 24 will have (re) liquefied the MCP of the first element 3a. And this can happen, even if the inner face of the first element 3a is doubled by an additional thermally insulating optional layer 5c.

Figures 5-7 have been developed on the same explanatory and operating principle as in Figure 4. The above is therefore applicable to them, with the following temperature values and their applications:

FIG. 5 applies to the case of a new generation battery operating at the optimum between 45 and 55.degree.

- Figures 6.7 apply to the case of a passenger compartment 1 whose temperature is to maintain summer (Figure 6) and winter (Figure 7) between about 20 and 25 ° C in the example.

In all cases, we find the particularities of temperatures T1 and T2 (see Figure 6 in particular).

In the case of the new generation battery operating at the optimum between 45 and 55 ° C, the second element 3b may comprise only one MCP material, for example at a phase change temperature of 45 ° C. below), since the maximum outside temperature defined here is 55 ° C and that T2 is equal to 50 ° C.

There are therefore cases where at least one of the barrier elements 3a, 3b can be monolayer and / or mono MCP.

Figures 6, 7, the arrows through the elements 3a, 5b, 3a indicate, facing a flow from the outside to the inside, the effects of thermal barrier at the indicated external temperatures (solid lines), but also the parts then inoperative (dotted), because of these same temperatures.

A start-up, for example a cold morning as in the case of FIG. 7, of the device 26 for internally heating the passenger compartment (volume 1), for example at 20 ° C., will again enable a hot flow 24, here air, to recharge, by liquefying, the "cold" MCP of the first element 3a inside thermal barrier. For example, an on / off switch and / or means for adjusting the temperature expected at the output of the heating device 26 are integrated to it to make the heat flow 24 only temporary.

Figure 15 now, schematized the use of the wall 6, provided with the first and second elements 3a, 3b of thermal barrier, as a local protective shield, around a motor element, such as a cylinder head.

Each of the elements 3a, 3b contains several MCP materials in the example. And, as in other cases here presented, the interior volume 1 may be that of a separate element, separated from the wall 6, as here

10 the motor element concerned. Thus, a thermally conductive wall 55, such as the metallic one of this motor element, could be interposed between the inner element 3a of the wall 6 and the volume 1. In general, the heat exchange could therefore be indirect between the inner element 3a of the wall 6 and the volume 1.

It will then be possible for this wall 55 of the motor element to define the means for temporarily supplying thermal energy, favoring the liquefaction of the MCP materials of the first element 3a, by heat exchange with them. It can indeed be considered that, when the engine is running, this energy can be brought to 55-60 ° C in this volume (or even

Significantly more), therefore at a higher temperature both at the state change temperatures of the PCMs 30a, 30b (assumed to be respectively at 35 ° C and 45 ° C) than at that to be maintained in the volume 1 (at about 50 ° C). C) when the engine is stopped and within 30-60mns, we want to restart it with the best efficiency while a

25 winter cold (0 ° C) is installed outdoors.

In the particular case of the aforementioned shield, the outer element 3b will typically aim to protect against cold, the inner member 3a acting as a temperature increase accelerator in the volume 1 and the wall 55, in the case of above an engine restart after a shutdown of

30 60mns or less. It is therefore pos- sible to favor state-change temperatures between -20 ° C and 30 ° C in the outer element 3b and between (30 or 35 ° C) and 45 ° C in the inner element 3a, with thermal insulation 5b interposed between them.

Suppose the engine has been running for several hours. He is hot. As long as the temperature in the wall 55 remains around 95 ° C, the assumed operating temperature, the MCP materials of the inner member 3a are liquid. Those of the outer element 3b are also liquid, because of the contribution of the energy Q brought to more than 40 ° C in the external environment 4 by the operation of the engine.

When the engine is stopped and the vehicle is parked at 0 ° C in the example, some (one in the example) MCP materials of the barrier 3b pass solid. This slows or delays the internal cooling of the wall 6. Idem in the inner element 3a: the MCP crystallized, releasing their hot energy, and thus having slowed down the cooling in 1 and 55.

When the engine, which has cooled, restarts, as soon as the temperature of the wall 55 reaches then exceeds 35 ° C and then 45 ° C, the PCM of the inner element 3a liquefy again. The wall 55 remains around 90-120 ° C, range of nominal temperatures assumed.

Yet another possible application of the thermal barrier 3 may be in the embodiment of a sleeve 40 of the type shown diagrammatically in FIGS. 8 and 9 exposed, around it, to a variable temperature environment 4 surrounding a central block 1 transversely to a reference axis 41.

The central block may for example be a drug container to be kept at low temperature, for example between 1 and 5 ° C, or be defined directly by the internal volume of this container, all or part of the walls would integrate in their thickness the barrier 3 Another hypothesis would be the keeping warm, for example between 25 and 45 ° C, of food in a box of which all or part of the walls would again integrate in their thickness said barrier 3. An isothermal holding of the block 1 via a housing heat-insulated thermal barrier 3 can therefore be targeted. In fact, the barrier position 3 will define the relative position (more inside or outside) of the hot and cold MCPs 3a, 3b and the location of the thermally insulating layer (s) 5a, 5b, depending the direction of the thermal gradient between interior 1 and exterior 4.

The two sleeves 40 shown schematically in FIGS. 8, 9 are formed from a strip of articulated panels with continuous thermal insulation, represented in an operational state, closed on itself.

Each comprises a series of barrier pockets 13 joined in pairs by flexible (or conformable) intermediate portions 15 where two successive pockets can articulate relative to one another.

In one of the cases (FIGS. 9, 10), there is, between two such articulation zones, a bulging portion 42 that is thermally insulating (at least).

In the other case (FIGS. 8, 11), said intermediate portions are entirely defined by a structure 43 with at least one heat-insulating material (x) 45 (preferably porous to be integrated with a global PIV structure), ensuring a continuity of thermal insulation between two successive pockets 13. The material 45 may be identical to the (x) insulating material (s) thermal (s) porous layers 5a and / or 5b.

In the image of the peripheral envelope that will maintain and join the different layers of barrier 3 above, these layers of thermally insulating materials and based on MCP hot and cold (such as in the example of Figures 10-13 layers 3a, 5b, 3b) are completely enclosed in one or more conformable sheets 49 of a single envelope (FIGS. 10-12) or double (FIG. 13). The sheets 49, metal or plastic, are sealed together (for example welded) over the entire periphery of said layers of materials, for sealing and the PIV constitution a priori desired envelope 51. The sheet (s) of a few tenths of a mm to a few mm thick will envelop, preferably in one piece, the pockets 13 and the connecting portions 15. A solution may therefore be, for the envelope 51 , to make at least a first inner envelope 51 has sealed (each) a thermally insulating layer (5a, 5b), the whole being, with the layers (3a, 3b) based on MCP, contained in a second outer envelope 51b not necessarily sealed (Figure 13).

In the example of Figure 11, the porous material (here plate-shaped) of each flexible structure 43 is interrupted in the porous thermal insulating material 5b which fills the pockets 13. There could, however, continuity.

To produce the intermediate portions of material 45, it will be possible in particular to use a flexible polymer mesh matrix of a few mm thick impregnated with an organic airgel, for example silica, or its pyrolisate (pyrolysed airgel, being specified that this alternative pyrolisate applies to each case of the present description where a porous thermally insulating material is concerned).

In the example of Figures 10-13, the hinge portions 15 are each defined by the sheets 49 contiguous for example by the internal vacuum created. The bulged portions 42 (FIG. 10) contain at least one thermally insulating layer 53, or even at least one MCP layer.

Thicker than the impregnated fabrics of FIG. 11, for example more than 2.5 to 3 times thicker, as shown schematically, the pockets 13 will typically be stiffer than the hinge structures 15.

Typically, a pocket 13 with nano-porous aerogels core material or their pyrolisate and therefore hot and cold MCP may have a thermal conductivity of less than 100 mW.m-1 .K-1 at 20 ° C for an internal pressure of 2 at 5 to 10 ^"3 Pa. The depression in the pockets, or even the portions 21, may be that of the usual VIPs: 10 ^{" 2} to 10 ^"3 Pa.

To keep closed each band forming the sleeve 40, one can provide a fastening system at two opposite ends of the strip, with a detachable Velcro ® type connection, for example. At the location of its open ends, each sleeve will favorably, as shown schematically in FIG. 6, covers 490 provided with at least one thermal insulator 51, or they themselves also each of a barrier 3.

A housing 53 forming a barrier to an autonomous thermal management system can thus be established around a block 1 whose temperature is to be managed. And the use of PIV with porous insulating complex / MCP hot and cold should achieve a thermal resistance R = 5 m ² .K / W with only 35 mm of insulation.

The hot MCP (s) are interesting in this case, especially in the stopping phase of the engine. When the system descends in temperature due to the external temperature conditions lower than the temperature of the volume 1, a temperature step is marked at the change temperature of the (each) MCP present. BcI can delay the transfer of heat flow compared to a solution without MCP. At engine restart, the hot MCP (s) contribute to a faster rise in temperature of the engine block, but to a lesser extent.

As explained above, the hot and / or cold MCPs will preferably be respectively dispersed, for the first on one side, for the second on the other side of the thermally insulating intermediate layer 5b, in a matrix 28, typically a composite thermoplastic or an elastomeric matrix.

Hereinafter, an example of hot MCP and cold MCP elements, respectively, is provided for a battery operating favorably between 25 ° C and 35 ° C.

It may in particular be encapsulated MCP arranged, typically dispersed, in a matrix or support, which may be an elastomer, a silicone, or derivatives, EPDM (ethylene-propylene-diene monomer) or HNBR (hydrogenated butadiene-acrylonitrile copolymers) , also called "hydrogenated nitrile rubbers") or NBR (butadiene-acrylonitrile copolymers, also called "nitrile rubbers"). EP2690137 and EP2690141 give examples.

It should be noted however that any MCP may have a phase or state change at a predetermined temperature peak or which is established over a more or less wide temperature range. Thus, with a pure MCP (such as a paraffin) the change of state temperature will be constant, while it may be non-constant with several MCP, such as for a mixture of paraffins.

In general, the two cases that may be encountered in the present application in connection with the MCP (s) provided, any MCP change of state temperature here will be to consider in a range of 10 ° C, and typically to +/- - 5 ° C.

Claims

1. Thermal barrier (3) for promoting, in an internal volume (1) and / or opposite an element (2) disposed therein, maintaining a temperature in a predetermined range while the barrier is placed in an external environment (4) subjected to a non-constant temperature, characterized in that it comprises, from the inside, where is situated the internal volume (1) or the element which is arranged there, towards the outside where is said external environment (4):

a first element (3a) containing at least one MCP material storing or transferring thermal energy by state change and having a first state change temperature (Tf), and then

a second element (3b) containing at least one MCP material that stores or transfers thermal energy by a change of state and that has a second change of state temperature (Te), the second change of state temperature being different from the first,

and a third element, thermal insulator, (5a, 5b) disposed between the first and second elements containing a MCP material, or outside said second element (3b).

2. thermal barrier (3) according to claim 1, wherein at least one of the first element (3a) and second element (3b) of thermal barrier contains several MCP materials storing or transferring thermal energy by phase change, between liquid and solid, and having different state change temperatures.

3. Thermal barrier (3) according to one of the preceding claims, wherein:

the third element, thermal insulator, (5b) is arranged between the first and second elements, respectively inside and outside of thermal barrier (3a, 3b),

and the change of state temperature (s) of the MCP material (s) of the first element (3a) is (are) lower than the temperature (s) for changing the state of the MCP material or materials of the second thermal barrier element (3b),

such that at certain temperatures heat flows from outside and reaching one and / or the other of said elements are retarded in their progression from the outside to the inside, by a change of state of the (s) MCP in the said element (s) affected.

4. Thermal barrier (3) according to claim 3, wherein the at least some of the change of state temperature (s) of the MCP material (s) of the first element (3a) is (are) lower than the temperatures of said predetermined range. temperature to maintain.

5. thermal barrier (3) according to one of claims 1 to 3, wherein the highest temperature of change of state (T1) in said first element (3a) is equal to less than 5 ° C or so, at the lowest temperature of said predetermined temperature range to be maintained, and / or the lowest state change temperature (T2) in said second element (3b) is equal, to within about 5 ° C, at the highest temperature of said predetermined temperature range to be maintained.

6. thermal barrier (3) according to one of claims 1 or 2, wherein:

the change of state temperature (s) of the MCP material (s) of the first element (3a) is (are) greater than the temperature (s) of change of state of the MCP material or materials; second element (3b), for braking, by change of state, a heat transfer from the inside to the outside resulting from the supply into the internal volume of a fluid at at least a temperature greater than or equal to that ( s) change of state of the MCP material (s) of said first element (3a), thus favoring a rise in temperature in the interior volume,

and the third element, thermal insulation, (5b) is disposed between the first and second elements respectively inner and outer thermal barrier (3a, 3b).

7. An assembly comprising at least one volume (1) surrounded by a wall (6) provided with the thermal barrier (3) according to one of the preceding claims which surrounds said volume (1).

8. An assembly according to claim 7, comprising means 5 (20,22; 24; 26) temporary supply in said inner volume (1) of a thermal energy, in heat exchange with said first element (3a) containing at least one MCP material, to then promote a phase change of said MCP material of the first element (3a).

9. An assembly according to claim 7 or 8, wherein said inner volume 10 contains, as said element (2) disposed therein, cells (2) of electric battery producing heat whose temperature is to be regulated.

10. An assembly comprising at least one battery cell (2) having an outer casing (8) which is provided with the thermal barrier (3) according to one of claims 1 to 5.

1 1 .A set according to one of claims 7 or 8 wherein the thermal barrier (3) is intended to be placed in a said external environment (4), such as the environment of a heat engine:

- Periodically hotter than the change of state (s) between solid and liquid, or MCP material of the second element

20 (3b),

and with which this or these MCP materials of said second element (3b) are placed in heat exchange,

to then promote liquefaction of this or these MCP materials of said second element (3b).

An assembly according to claim 8, wherein the temporary thermal energy supply means (20,22; 24; 26) and said interior volume (2) communicate such that said energy is supplied in this volume to an temperature greater than or equal to the changeover temperature (s), between solid and liquid, of the MCP material (s) of the

First element (3a), in heat exchange with this or these MCP materials, to then promote their liquefaction.

13. An assembly according to one of claims 8 to 12, wherein at least one of the first and second elements (3a, 3b) comprises a plurality of MCP materials having different state change temperatures from each other and which are dispersed in a matrix (28) or arranged in several layers of materials each containing a said MCP material.

14. A method of thermal management of a volume, or an element disposed therein, surrounded by a thermal barrier (3), characterized in that:

the thermal barrier (3) according to one of claims 1 to 6 is produced,

and said thermal barrier (3) is arranged around said internal volume, or the element disposed therein, so that said first (3a) and / or second (3b) thermal barrier elements (3a, 3b) brake (nt) ), by changes of state, a heat flow coming from the outside.

15. A thermal management method, in an assembly according to one of claims 7 to 13, of an interior volume (1), or an element (2) disposed therein, characterized in that:

the thermal barrier (3) according to one of claims 1 to 7 is produced with phase-change MCP materials between liquid and solid,

said heat barrier (3) is arranged around said internal volume, or the element disposed therein, so that said first (3a) and / or second (3b) thermal barrier elements (3a, 3b) brake (s) , by changes of state, a heat flow coming from the outside,

and, once the change in states of said at least one MCP material of the first thermal barrier element (3a) is achieved, a new change in its state is favored by a temporary supply of thermal energy from said means (20, 22 24; 26) temporary supply of thermal energy.